Review on Nenesupply 9Oz Wide Mouth Feeding And Storage Bottle Compatible With Spectra S2, S1, And 9 Plus Pumps - Includes Nipple, Sealing Disc, And Compatible With Spectra S2 Accessories And Pump Parts by Polo Bradley

We bought these for preparing and storing small batches of formula and they work great for us. We had a few different brands of 8-9oz bottles before this and all of them required 2 pieces to make a cap that gave a sealed, leak-proof travel/storage option—and they were all kinda tricky to actually get on right so that the bottle was actually leak proof. I guess the caps for these are also technically 2-pieces but the clear rubber ring that fits into the cover cap to create the seal fits in the cover cap more like a rubber washer or gasket that stays securely in place—see pictures, you wouldn’t notice the ring unless you were looking for it. It seems like it would take some effort to remove the ring but we haven’t tried. It looks like Id need a knife or flathead screwdriver to pop it out from its place inside the cover cap.this might be a ‘bug’ for some people depending on how you plan to use these, but it’s definitely a ‘feature’ for us.